1. Field of the Invention
The present invention relates to a governor cap sealing structure of a transmission gearbox.
2. Description of the Prior Art
In a conventional automatic transmission gearbox, as shown in FIGS. 1 and 2, a governor valve 1 for producing a pressure signal corresponding to an automobile speed is connected to and is rotated by an output shaft of the transmission gearbox through a pair of gears 2a and 2b and a governor shaft 3 to produce a governor pressure corresponding to the automobile speed. The governor valve 1 is normally arranged outside a transmission case 4, and a governor cap 5 is required to cover the governor valve 1 in order to prevent the oil flowing out of the governor valve 1 from the scattering in all directions during the rotation thereof. Hence, the governor cap 5 is mounted to a mount member 7 attached to the outside of the transmission case 4 through a sealing ring 6, which is made of a resilient material such as rubber, interposed therebetween for sealing the space between the governor cap 5 and the mount member 7, as hereinafter described in detail.
In a conventional governor cap sealing structure employed in an automatic Trans-axle (Trade Name), as shown in FIG. 2, the governor cap 5 includes a shoulder portion 5a, a cylindrical portion 5b and a bottom portion 5c, and the mount member 7 includes an outer sealing surface 7a, an intermediate flange portion 7b projecting outward, and an end surface 7c. The sealing ring 6 is correctly fitted in a sealing space 8 defined by the shoulder portion 5a of the governor cap 5 and the outer sealing surface 7a of the mount member 7, and the governor cap 5 is prevented from its falling from the mount member 7 by a clip 9 attached to the bottom portion 5c of the governor cap 5.
In this embodiment, however, the width of the outer sealing surface 7a of the mount member 7 is smaller than that of the sealing ring 6, and hence, even when the sealing ring 6 is exactly arranged in the sealing space 8, the sealing ring 6 partially protrudes beyond the end surface 7c of the mount member 7. Further, when the sealing ring 6 is insufficiently or incompletely fitted in the sealing space 8, as shown by the sealing ring 6a indicated by the one-dotted line in FIG. 2, it is liable to misunderstand such an insufficient or incomplete arrangement of the sealing ring 6 for the correct fitting. Then, when the governor cap 5 is mounted to the mount member 7 while the sealing ring 6 is insufficiently or incompletely fitted in the sealing space 8, the sealing ring 6 is caught by the shoulder portion 5a of the governor cap 5 and the end surface 7c of the mount member 7, and is deformed thereby, resulting in a cause of a problem such as an oil leakage.